+// vim:ts=8:expandtab
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
*
*/
const char *get_ipv6_addr() {
- static char buf[INET6_ADDRSTRLEN+1];
- struct addrinfo hints;
- struct addrinfo *result, *resp;
- int fd;
-
- memset(&hints, 0, sizeof(struct addrinfo));
- hints.ai_family = AF_INET6;
-
- if (getaddrinfo("k.root-servers.net", "domain", &hints, &result) != 0) {
- perror("getaddrinfo()");
- return "no IP";
- }
-
- for (resp = result; resp != NULL; resp = resp->ai_next) {
- if ((fd = socket(resp->ai_family, SOCK_STREAM, 0)) == -1) {
- perror("socket()");
- continue;
- }
-
- if (connect(fd, resp->ai_addr, resp->ai_addrlen) == -1) {
- perror("connect()");
- continue;
- }
-
- struct sockaddr_storage local;
- socklen_t local_len = sizeof(struct sockaddr_storage);
- if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
- perror("getsockname()");
- return "no IP";
- }
-
- memset(buf, 0, INET6_ADDRSTRLEN + 1);
- int ret;
- if ((ret = getnameinfo((struct sockaddr*)&local, local_len, buf, sizeof(buf), NULL, 0, NI_NUMERICHOST)) != 0) {
- fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
- return "no IP";
- }
-
- (void)close(fd);
-
- free(result);
- return buf;
- }
-
- free(result);
- return "no IP";
+ static char buf[INET6_ADDRSTRLEN+1];
+ struct addrinfo hints;
+ struct addrinfo *result, *resp;
+ int fd;
+
+ memset(&hints, 0, sizeof(struct addrinfo));
+ hints.ai_family = AF_INET6;
+
+ /* We resolve the K root server to get a public IPv6 address. You can
+ * replace this with any other host which has an AAAA record, but the
+ * K root server is a pretty safe bet. */
+ if (getaddrinfo("k.root-servers.net", "domain", &hints, &result) != 0) {
+ perror("getaddrinfo()");
+ return "no IP";
+ }
+
+ for (resp = result; resp != NULL; resp = resp->ai_next) {
+ if ((fd = socket(resp->ai_family, SOCK_DGRAM, 0)) == -1) {
+ perror("socket()");
+ continue;
+ }
+
+ /* Since the socket was created with SOCK_DGRAM, this is
+ * actually not establishing a connection or generating
+ * any other network traffic. Instead, as a side-effect,
+ * it saves the local address with which packets would
+ * be sent to the destination. */
+ if (connect(fd, resp->ai_addr, resp->ai_addrlen) == -1) {
+ /* We don’t display the error here because most
+ * likely, there just is no IPv6 connectivity.
+ * Thus, don’t spam the user’s console but just
+ * try the next address. */
+ (void)close(fd);
+ continue;
+ }
+
+ struct sockaddr_storage local;
+ socklen_t local_len = sizeof(struct sockaddr_storage);
+ if (getsockname(fd, (struct sockaddr*)&local, &local_len) == -1) {
+ perror("getsockname()");
+ (void)close(fd);
+ return "no IP";
+ }
+
+ (void)close(fd);
+
+ memset(buf, 0, INET6_ADDRSTRLEN + 1);
+ int ret;
+ if ((ret = getnameinfo((struct sockaddr*)&local, local_len,
+ buf, sizeof(buf), NULL, 0,
+ NI_NUMERICHOST)) != 0) {
+ fprintf(stderr, "getnameinfo(): %s\n", gai_strerror(ret));
+ return "no IP";
+ }
+
+ free(result);
+ return buf;
+ }
+
+ free(result);
+ return "no IP";
}